[views/templates] provide a modal main template (closes #3274672)
The current NonTemplatableViewTemplate may seem to provide the desired
feature if a '__notemplate' is provided in the form, unfortunately,
it:
* wraps the view in a spurious div
* calls view.set_stream(), which has the effect of wiping any js/css
resource recorded until then by the view, leading to hard-to-track
missing resources symptoms
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')